German Unexamined Application DE 101 26 286 A1 to Engelhardt, et al. discloses a method and an apparatus for point-by-point scanning of a sample. The method is characterized by the steps of generating a setpoint signal for each scan point and transferring the setpoint signal to a scanning device. In further steps, an actual signal is ascertained for each scanned point from the position of the scanning device. Also performed are detection of at least one detected signal for each scanned point, calculation of a display signal and an image position from the actual signal and/or the setpoint signal and the detected signal, and allocation of the display signal to the image point position. It is problematic that conventionally, deflection of the mirror galvanometer proceeds, for example, sinusoidally, i.e. the deflection changes more slowly in the vicinity of the reversing points (corresponding to the image edges) than at the zero transition. This nonlinearity results in a different illumination time or cycle time Ti for each pixel (see FIG. 4). Conventionally, the signals generated by the detector are integrated, using an integrator constructed with analog technology, over a constant maximum time suitable for all pixels. The data value is then read out by an analog-digital converter, and the integrator is cleared. Only then does a new cycle begin for the next pixel. It is disadvantageous here that the integration time is based on the pixels having the shortest illumination time or cycle time. Valuable measurement time is thus lost for the pixels at the image edges (scan direction reversal) having longer cycle times, i.e. the signal-to-noise ratio there is degraded.
Unexamined Application DE 197 02 752 A1 to Schoppe, et al. discloses a triggering system for a scanner drive. The scanner is driven by an oscillating motor, so that a scanning mirror oscillates. A triggering unit provides linear feed of a suitable control frequency to the oscillating motor, so that the scanning beam also describes a substantially linear path on the surface of the sample.
European Patent Application EP 0 845 693 to Hakozaki encompasses a confocal microscope and a method for generating a three-dimensional image with a confocal microscope. A device is provided that generates a relative motion in the direction of the optical axis. Also provided is a control unit that simultaneously controls or regulates the device for generating the relative motion and a scanning device.
Further disadvantages of the existing art are that an input signal cannot be detected during the necessary clearing time of an analog integrator. At high scanning rates, however, the clearing time can constitute more than half the cycle time. At 8 kHz (resonant scan), for example, the integration time per pixel can be 25 ns. Clearing of the integrated signal (for short integration times), on the other hand, can take at least 20 ns. Because a high scanning speed is required, however, it is no longer possible to completely clear the integrator. For this reason as well, the integration time (and thus also the cycle time) must be constant within a line that is to be scanned. The final integration value, and thus also the subjective image brightness, is thus dependent on the scanning speed and the scan format. The image settings must be correspondingly corrected by the user.